#include <stdio.h>

int main() {
    int s, e;
    scanf("%d %d", &s, &e);

    int sh = s / 100, start_minute = s % 100;
    int eh = e / 100, end_minute = e % 100;

    int st = sh * 60 + start_minute;
    int et = eh * 60 + end_minute;

    int d = et - st;
    int dh = d / 60;
    int dm = d % 60;

    printf("%02d:%02d\n", dh, dm);

    return 0;
}
